One of the ways you can navigate to the store is by locating your balance in the top left of your game and tapping or clicking on the "+" symbol.  This will take you to the store where you can choose from a variety of different packages.

You can also go to your game menu, by clicking on the hamburger menu at the top right corner of your game, and the drop down menu will display "Store".  You can click or tap to be brought to the store.